Tesi etd-09012021-141316 |
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Tipo di tesi
Tesi di laurea magistrale
Autore
CUCELI, FRANCESCO
URN
etd-09012021-141316
Titolo
Application of Fuel Performance Models for Fast Reactor Transient Analyses
Dipartimento
INGEGNERIA CIVILE E INDUSTRIALE
Corso di studi
INGEGNERIA NUCLEARE
Relatori
relatore Prof. Forgione, Nicola
Parole chiave
- SFR
- SIMMER III
- SODIUM FAST REACTOR
- TRANSURANUS
- ULOF
- UTOP
Data inizio appello
27/09/2021
Consultabilità
Non consultabile
Data di rilascio
27/09/2091
Riassunto
This work concerns the assessment of the consequences of a Loss Of Coolant Accident (LOCA) and an Unprotected Transient Over Power (UTOP) in a fuel pin of a Sodium-cooled Fast Reactor in the framework of the Phase 2 of the OECD/NEA/EGIF Benchmark study of the fuel performance codes. The analysis focuses on the behavior of a single Mixed oxide fuel (MOX) design in steady-state and transient conditions. The pin is foreseen to be irradiated for 5 cycles, with the duration of a cycle corresponding to 410 days. The study was carried out on a fuel pin with the clad in 15-15Ti.
The first part of this work analyzed the pin behavior in stationary conditions, imposing benchmark data for the axial power and imposing a difference between the inlet temperature and the outlet temperature of the outer cladding of 150 degrees. The analysis was performed with the fuel performance code TRANSURANUS. According to the simulation, after around 30000 hours the clad starts to reopen for the excessive swelling, decreasing the gap conductance and increasing the fuel center temperature up to fusion values. According to our simulation, this material seems to not be able to sustain the irradiation levels provided in this benchmark. One of the most significant phenomena leading to pin failure is a vacation swelling of clad material.
The second part of this work evaluated the behavior of the irradiated pin under transient conditions, with the calculation of a UTOP and a ULOF transient, performed with the safety code SIMMER. As input data, the results obtained from the TRANSURANUS simulation were used and selected in the worst conditions for the fuel pin. The result obtained is satisfactory, for UTOP the more critical issue is the maximum fuel temperature because the core power increases immediately at beginning of the transient. However, the maximum fuel temperature is below the melting temperature. During the ULOF transient the temperatures of fuel, cladding and coolant increase at a low pace and, after about 150 s of transient, all remain within safety limits.
The first part of this work analyzed the pin behavior in stationary conditions, imposing benchmark data for the axial power and imposing a difference between the inlet temperature and the outlet temperature of the outer cladding of 150 degrees. The analysis was performed with the fuel performance code TRANSURANUS. According to the simulation, after around 30000 hours the clad starts to reopen for the excessive swelling, decreasing the gap conductance and increasing the fuel center temperature up to fusion values. According to our simulation, this material seems to not be able to sustain the irradiation levels provided in this benchmark. One of the most significant phenomena leading to pin failure is a vacation swelling of clad material.
The second part of this work evaluated the behavior of the irradiated pin under transient conditions, with the calculation of a UTOP and a ULOF transient, performed with the safety code SIMMER. As input data, the results obtained from the TRANSURANUS simulation were used and selected in the worst conditions for the fuel pin. The result obtained is satisfactory, for UTOP the more critical issue is the maximum fuel temperature because the core power increases immediately at beginning of the transient. However, the maximum fuel temperature is below the melting temperature. During the ULOF transient the temperatures of fuel, cladding and coolant increase at a low pace and, after about 150 s of transient, all remain within safety limits.
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